Opaque films with a thickness of from 10 to 500 μm are well known. None of the known films comprises any type of soluble flame retardant or any UV stabilizer as light stabilizer or any optical brightener, and neither the films nor items produced from them are therefore suitable for outdoor applications. In outdoor applications these films yellow, even after a short period, and their mechanical properties become impaired as a result of photooxidative degradation of the thermoplastic by sunlight. The films also fail to comply with the fire tests of DIN 4102 Part 2 and Part 1, and also fail the UL 94 test.
EP-A-0 620 245 describes films with improved heat resistance. These films comprise antioxidants suitable for scavenging free radicals formed in the film and for degrading any peroxide formed. However, this specification makes no proposal as to how the UV resistance of films of this type may be improved.
DE-A 23 46 787 describes a low-flammability polymer. Besides the polymer, the claims also cover the use of the polymer to give films and fibers. However, when films were produced from this phospholane-modified polymer the following shortcomings were apparent:
The polymer is very susceptible to hydrolysis and has to be very thoroughly predried. When the polymer is dried using dryers of the prior art it cakes, and if production of a film is possible at all it is possible only under very difficult conditions.
The films produced, under extreme and uneconomic conditions, embrittle at high temperatures, that is to say their mechanical properties decline sharply as a result of substantial embrittlement, making the film unusable. This embrittlement arises after as little as 48 hours at high temperature.